A magnetic resonance imaging (MRI) apparatus is an apparatus that acquires chemical and physical microscopic information on a substance by utilizing a magnetic resonance phenomenon. The magnetic resonance phenomenon is a phenomenon that, when a group of subject nuclear spins is placed in a magnetic field, the nuclear spins resonate with a radio frequency magnetic field that rotates at a certain frequency (referred to as a resonance frequency) corresponding to the unique magnetic moment of the nuclear spins and the intensity of a magnetic field in which the nuclear spins exist and accordingly a signal (referred to as a magnetic resonance signal) is generated in a relaxation process of the nuclear spins. In the MRI apparatus, adjusting the parameter values of imaging parameters that define pulse sequences that are used for imaging makes it possible to obtain images having various contrasts reflecting, for example, T1 and T2 that are relaxation times of tissue and the density of hydrogen nuclei (proton density).
Normally, in diagnosing with an MRI apparatus, a limited number of T1-weighted image and a T2-weighted image are obtained due to considerations of the examination time according to pre-set certain imaging parameters and then a diagnosis is made. Depending on the clinical condition, however, there may be a unique imaging parameter that enables not a pre-determined contrast image but the easiest identification of a lesion. Under the circumstances, there is a technology in which an MRI apparatus calculates, with respect to each pixel, for example, relaxation time, a density of hydrogen nuclei, and a strength of a radio frequency magnetic field from multiple sets of image data obtained from a subject and creates, through a calculation, an image in which the degree of T1 weighting and T2 weighting is changed after imaging.